In injection blow molding machines it is well known to provide a core rod that is inserted successively into an injection mold to form a preform or parison and is thereafter used to transfer the parison to a blow mold where the parison is blown outwardly against the confines of the mold to form the hollow article.
One type of injection blow molding machine includes a turret that has three surfaces, each of which supports a plurality of longitudinally spaced core rod assemblies. When the turret is rotated, the core rod assemblies are moved successively first to a station having an array of parison molds where the parisons are injection molded on the core rod assemblies, then to another station having an array of blow molds where the parisons are blown to form the hollow articles and finally to a station where the hollow articles are removed from the parisons permitting a new cycle to begin.
In such a machine it is necessary that the core rod have some limited longitudinal movement with respect to its support. Inasmuch as the core rod must be cooled by circulating coolant within the core rod, provision must be made for directing the coolant from a manifold to the core rod and returning the coolant to the manifold. In order to accommodate the longitudinal movement dynamic seals have been heretofore utilized, but these are subject to leakage and necessitate continuous maintenance.
Among the objectives of the present invention are to provide a core rod assembly which obviates the aforementioned problems; which is relatively simple; and which obviates the need for sliding parts or dynamic seals.
In accordance with the invention, the core rod assembly for injection blow molding machines comprises a plurality of hollow core rods each of which has a closed end and an open end which is threaded on a core rod spool that is telescopically received in a core rod body such that the core rod and core rod spool has limited longitudinal movement relative to the core rod body for the purpose of permitting blow air to be provided for blowing a parison on the core rod. A tube extends through an opening in each core rod spool and the opening core rod and the spool has laterally extending passages communicating with the exterior of the spool. The passages are connected to spaced passages of a manifold by bellows type adaptors such that temperature control fluid such as liquid or air can be circulated through the tube and thereafter about the tube to cool the core rod. The bellows type adaptors provide a seal which accommodates the limited longitudinal movement between the spool and the body without the need for dynamic seals or bulky hoses so that a greater number of molds may be utilized in side by side relation.